The fabrication processes used in making semiconductor devices have progressed rapidly to a point where highly complicated multifunction semiconductor chips can be reliably produced at a cost that is close to or even below the cost of a suitable housing. Accordingly, much attention has been given to automatic housing assembly processes. One of the more useful approaches is to fabricate a composite tape consisting of an insulating strip having a series of intermediate lead patterns located thereon. The lead pattern is in the form of metal fingers located on the insulating strip. The strip has indexing said transporting holes located along one or both edges. Indexed thereto are a sequence of lead pattern arrays. Each pattern has an array of conductive fingers, the inner ends of which are located so as to mate with the bonding pads normally employed to make connections to the conventional semiconductor chip devices. In current technology it is desirable to hold the positional tolerance of the metal fingers to 1 mil. Thus precision processing is required. The outer ends of the fingers extend to a position that registers with the conductors of the structure upon which the chip is to be mounted. This can be either a typical lead frame array useful in making transfer molded plastic housings or the pattern array on a printer wiring substrate such as is typically found in hybrid assemblies. The inner ends of the fingers are usually made to extend into an aperture prepunched in the insulating strip. The aperture is made slightly larger than the lead array of the semiconductor chip to be bonded.
In order to make chip contact the contacts are ordinarily bumped. In this approach the semiconductor chip, while still in wafer form, is processed to produce raised metal mounds or bumps on each of the bonding pads. This can be done by a combination of masking, metal deposition and metal etching. The bumps are typically gold or copper located on top of suitable metal barrier layers deposited on top of the conventional chip bonding pads. The metals are selected for low cost application, reliability, and ease of bonding. Typically the lead patterns are located in place over the bumped chips and are simultaneously thermocompression bonded to the bumps. The chip is then physically located and can be carried on the composite strip.
In typical high speed assembly the strips are fabricated in tape form that can be handled on reels. Automatic machinery can be used to fabriate the assembly tape. The tape can then be passed through an automatic chip bonder where each pattern picks up an associated chip. Then the tape is passed through an automatic machine that bonds the outer finger portions to either a lead frame or other substrate, again using thermocompression gang bonding.
U.S. Pat. Nos. 3,689,991 and 3,763,404 disclose a composite tape process. These patents disclose a prepunched insulating tape that has a layer of metal bonded thereto. The metal is then photolithographically etched to create the desired lead pattern.
Since the application of bumps to a semiconductor device involves cost and can adversely affect reliability, efforts have been made to bump the tape rather than the semiconductor device. U.S. Pat. No. 3,781,596 discloses a tape having a metal lead pattern wherein the inner ends of the fingers have a raised portion suitable for bonding to unbumped semiconductor chips. My copending application Ser. No. 921,642 filed July 3, 1978 and titled CONTROLLED COLLAPSE THERMOCOMPRESSION GANG BONDING discloses and claims an improved bumped tape.
To overcome some of the problems that attend the composite tape fabrication, the approach developed in my U.S. Pat. No. 4,063,993 has been employed. Here a copper tape is supplied with deposited rings of insulation to support the lead pattern which is etched into the copper tape.
The prior art approaches have proved to be useful but many problems still exist. It would be desirable to further lower cost, increase reliability, and increase production rates. It would further be desirable to employ a process that is amenable to the production of bumped tape having a suitable bump configuration as disclosed in my above mentioned copending application.